Re: [PATCH v2 12/16] powerpc/64e: remove mmu_linear_psize

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 21/10/2021 à 05:54, Nicholas Piggin a écrit :
> mmu_linear_psize is only set at boot once on 64e, is not necessarily
> the correct size of the linear map pages, and is never used anywhere
> except memremap_compat_align.
> 
> Remove mmu_linear_psize and hard code the 1GB value instead in
> memremap_compat_align.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   arch/powerpc/mm/ioremap.c    | 6 +++++-
>   arch/powerpc/mm/nohash/tlb.c | 9 ---------
>   2 files changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/mm/ioremap.c b/arch/powerpc/mm/ioremap.c
> index 57342154d2b0..730c3bbe4759 100644
> --- a/arch/powerpc/mm/ioremap.c
> +++ b/arch/powerpc/mm/ioremap.c
> @@ -109,12 +109,16 @@ void __iomem *do_ioremap(phys_addr_t pa, phys_addr_t offset, unsigned long size,
>   */
>   unsigned long memremap_compat_align(void)
>   {
> +#ifdef CONFIG_PPC_BOOK3E_64

I don't think this function really belongs to ioremap.c

Could avoid the #ifdef by going in:

arch/powerpc/mm/nohash/book3e_pgtable.c

and

arch/powerpc/mm/book3s64/pgtable.c

> +	// 1GB maximum possible size of the linear mapping.
> +	return max(SUBSECTION_SIZE, 1UL << 30);

Use SZ_1G

> +#else
>   	unsigned int shift = mmu_psize_defs[mmu_linear_psize].shift;
>   
>   	if (radix_enabled())
>   		return SUBSECTION_SIZE;
>   	return max(SUBSECTION_SIZE, 1UL << shift);
> -
> +#endif
>   }
>   EXPORT_SYMBOL_GPL(memremap_compat_align);
>   #endif
> diff --git a/arch/powerpc/mm/nohash/tlb.c b/arch/powerpc/mm/nohash/tlb.c
> index 5872f69141d5..8c1523ae7f7f 100644
> --- a/arch/powerpc/mm/nohash/tlb.c
> +++ b/arch/powerpc/mm/nohash/tlb.c
> @@ -150,7 +150,6 @@ static inline int mmu_get_tsize(int psize)
>    */
>   #ifdef CONFIG_PPC64
>   
> -int mmu_linear_psize;		/* Page size used for the linear mapping */
>   int mmu_pte_psize;		/* Page size used for PTE pages */
>   int mmu_vmemmap_psize;		/* Page size used for the virtual mem map */
>   int book3e_htw_mode;		/* HW tablewalk?  Value is PPC_HTW_* */
> @@ -655,14 +654,6 @@ static void early_init_this_mmu(void)
>   
>   static void __init early_init_mmu_global(void)
>   {
> -	/* XXX This will have to be decided at runtime, but right
> -	 * now our boot and TLB miss code hard wires it. Ideally
> -	 * we should find out a suitable page size and patch the
> -	 * TLB miss code (either that or use the PACA to store
> -	 * the value we want)
> -	 */
> -	mmu_linear_psize = MMU_PAGE_1G;
> -
>   	/* XXX This should be decided at runtime based on supported
>   	 * page sizes in the TLB, but for now let's assume 16M is
>   	 * always there and a good fit (which it probably is)
>